Cardiac complications and graft thrombosis are frequent and serious complications after vascular surgery. The work described herein consists of four experiments, which seek to characterize and reduce such morbidity. The first series will seek to show that clonidine, at higher doses, can suppress the adrenergic response to surgery without causing undue hemodynamic instability. The second experiment will test the hypothesis that intensive sympatholysis will decrease the normally high incidence of postoperative myocardial ischemia. The third investigation will seek to show that clonidine, despite its alpha-2 agonists properties, reduces the postoperative hypercoagulable response in vascular surgery patients. Lastly, the ability of coagulation, as measured by fibrinogen levels and whole-blood aggregometry, to predict myocardial ischemia and vascular graft thrombosis after vascular surgery will be investigated. These studies should provide insight into future therapies which may improve functional outcome in this high-risk group of patients.